The invention relates to a spinning or twisting spindle assembly having a spindle shaft which is rotatably supported inside a spindle bearing housing by means of a neck bearing and a step bearing assembly.
In use, a large number of similar spindle assemblies of the type contemplated by the invention are attached to spinning or twisting machine frame members (spindle rails) and are rotatably driven by a tangential belt. The tangential belt extends adjacent the spindle assemblies and drivingly engages driving wharves carried on respective spindle shafts of the spindle assemblies. It is not uncommon for several hundred common belt driven spindle assemblies to be provided at one side of a spinning or twisting machine.
Increasing rotational speeds of the spindle shafts, which are desirable in terms of increases in productivity, create increasing noise problems. It has been discovered that a significant source of these noise problems emanates from the roller bodies of the neck bearings which radially support the rotating spindle shaft at an axial position close to the belt driven wharve and axially spaced from the bottom end of the spindle shaft supported in the step bearing assembly at the bottom of the spindle bearing housing.
In conventional commercially available spindle assemblies, such as the Sussen spindle bearing HP-S 68, manufactured and marketed by the Sussen Group of Germany, the spindle bearing housing is inserted through an opening in a spindle rail member and is threadable clamped directly to the rail by a spindle flange assembly. It has been discovered that the vibrations generated at the roller bodies of the neck bearing in such prior art constructions are transmitted as structure-borne noise or vibrations by way of the spindle bearing housing which forms or is fixed to the outer bearing race of the neck bearing. These vibrations are transmitted directly to the spindle flange assembly and the spindle rail due to the direct clamping connection of the spindle bearing housing. These vibrations are converted into sound causing mechanical vibrations of the large-area machine elements, including the spindle rail and machine frame supports for the spindle rail. Thus, although spinning or twisting spindles and their bearings can be manufactured with increased precision by modern machinery and manufacturing methods, noise problems as discussed above become particularly troublesome starting at rotational speeds of 17,000 min.sup.-1 (revolutions per minute).
In the case of a known spinning or twisting spindle of the initially mentioned type (EP-A 209 799), a holding device for the spindle bearing housing comprises a sleeve mounted on the spindle bearing housing in the area of the step bearing and a sleeve which is arranged at an axial distance to it, surrounds the spindle bearing housing at a distance and is used for the fastening to a spindle rail. A ring of axially extending flexible spring bars arranged at a uniform distance is provided between the two sleeves. As a result, it is to be achieved that the spindle bearing housing can be deflected only radially with respect to the spindle axis.
In order to reduce the running noises of spinning or twisting spindles, it is also known from German Patent Document DE-A 36 20 497 to mount the spindle bearing housing by means of rubber-elastic damping elements on a spindle rail. Although this achieves a reduction in the generating of noise, it is connected with other functional disadvantages. It is an important disadvantage that there is the risk that the rubber-elastic damping element, when it is loaded on one side, which occurs particularly in the case of a tangential-belt drive for the spindles, yields more and more as the time goes by so that the spindle will be skewed.
A spindle assembly of the initially mentioned type as it is known from the German Patent Document DE-C 27 49 389 also does not adequately solve the above-discussed noise problems. In this construction, a bearing housing is provided which accommodates a neck bearing and a complete step bearing (a radial bearing element as well as an axial bearing element) and thus holds the whole spindle also in the axial direction. In this construction, the bearing housing is mounted closely below the neck bearing on the upper end of an intermediate tube which surrounds the bearing housing at a distance in the remaining area. Below the step bearing, the intermediate tube is connected with its lower end by way of a connecting element with the lower end of an outer bearing housing which is provided with devices for the fastening to a spindle rail and which surrounds the intermediate tube at a distance. In one embodiment, the bottom part has a contraction in order to create an area that is spring-elastic when being bent. The spaces between the bearing housing and the intermediate tube, on the one hand, and between the intermediate tube and the outer bearing housing, on the other hand, are connected with one another by way of openings and are filled with oil, the level of which extends along half the height of the outer bearing housing. By means of this oil, vibrations of the spindle are to be damped so that the running quality of the spindle will be improved.
Measures for the reduction of noise are not provided in the case of this spindle assembly disclosed in German Patent Document DE-A 27 49 389. The existing contraction in the connecting element does not act as a point of discontinuity by means of which the structure-borne sound transmission is limited to a significant extent. The reason is that the space between the intermediate tube and the outer tube is filled with oil also in the area of the contraction so that a structure-borne noise transmission takes place by way of this oil.
It is an object of the invention to develop a spinning or twisting spindle assembly of the initially mentioned type such that a clear reduction of the noise problem is achieved.
This object is achieved according to preferred embodiments of the invention by providing an outer housing clamped directly to the spindle rail, a bearing housing disposed inside of and vibration isolated from the outer housing by way of an annular gap along the length of the bearing housing from a neck bearing to below a step bearing, and a vibration isolation connection of the outer housing and bearing housing at a position below the step bearing, whereby vibrations at the neck bearing are transmitted only indirectly to the spindle rail by way of downward transmission through the bearing housing to the vibration isolation connection and then upward through the outer housing back up to the spindle rail.
In certain preferred embodiments, the vibration isolation connection is a direct metallic connection. This direct metallic connection is preferably made by press fitting the bottom of the bearing housing into the bottom part of the outer housing. In alternative embodiments, a metallic connecting element is press fit into the bottom of the bearing housing and into the bottom part of the outer housing. A significant advantage of a direct metallic connection between the bearing housing and outer housing is that such direct metallic connection accommodates the transverse loading of the spindle shaft and bearing housing by the driving belt over long periods of time. Rubber elastic type connection are disadvantageous in that, over time, the transverse loading causes a change in the elastic characteristics so that the operation of the spindles over time may not remain reliable. That is, rubber elastic connections deteriorate over time while the metallic connections do not. The metallic connections still provide elastic flexibility due to their shape and materials as compared to the bearing housing and outer housing being connected.
In certain preferred embodiments of the invention, the vibration isolation connection includes a diminished cross-section of the bottom part of the bearing housing constructed as a discontinuity point which limits transmission of structure-borne noise and which, with respect to the flexural strength, in the case of a radial load at the neck bearing, has a spring rate of 70 N/mm to 300 N/mm. In certain preferred embodiments of the invention the space between the spindle bearing housing and the outer housing, which space is separated from the interior of the spindle bearing housing, a sound insulating medium is present, the sound velocity of which is preferably less than 500 m/s. Because of the discontinuity point, the structure-borne sound transmission is largely interrupted as early as inside the spindle bearing housing so that high-frequency vibrations which later become sound are transmitted only to a minor extent to the outer housing and from there to the spindle rail and other machine parts. The outer housing itself also causes a shielding of the sound emitted by the spindle bearing housing. In this case, it is also provided that no medium is present in the space between the spindle bearing housing and the outer housing which is capable of transmitting structure-borne sound to a significant degree. That is, the sound insulating medium is not a fluid like lubricating oil usually present inside the bearing housing, which lubricating oil would be capable of and would transmit structure-borne sound to a degree not intended by the present invention.
In especially preferred embodiments where sound insulating medium is filled into the space between the bearing housing and outer housing, the sound insulating medium is filled to a level at least two-thirds of the height of the spindle bearing housing and the sound insulating medium is viscous between 20.degree. C. and 60.degree. C.
In certain preferred embodiments of the invention, it is provided that the space between the spindle bearing housing and the outer housing is filled with a grease at least in the area of the discontinuity point. As a result, the generating of noise can be further reduced. A similar effect is obtained if the space between the spindle bearing housing and the outer housing is filled with an elastomer at least in the area of the discontinuity point.
In certain preferred embodiments of the invention, it is provided that the step bearing is divided into a radial bearing element and an axial bearing element and that the axial bearing element is supported in an axial direction with respect to a connecting element forming the vibration isolation connections. As a result, it is achieved that the spindle bearing housing in its tube-shaped area is not loaded by tensile forces or pressure forces but only by bending forces. This will result in more defined conditions also with respect to the discontinuity point.
The invention is first based on the recognition that the main cause of the running noises is the neck bearing which normally contains roller bodies engaging the spindle shaft. Even if the neck bearing has a high precision of shape and only a small play is maintained in the area of the neck bearing, small deviations of the running surface cannot be avoided due to the asymmetric transverse loading by the driving belt, which have the result that the roller bodies and thus also the spindle bearing housing are caused to perform vibrations. These vibrations are then, in a so-called flow of structure-borne sound, transmitted to other machine elements which have larger surfaces capable of vibrating and correspondingly increase the generating of noise. By means of the point of discontinuity formed by the vibration isolation connection of the bottom of the bearing housing to the outer housing, it is achieved that the flow of structure-borne sound is reduced significantly so that vibrations of the spindle bearing housing are transmitted to other machine elements and particularly the spindle rail only to a significantly reduced extent. The running noises are therefore essentially reduced to the spindle bearing housing as the source of noise. In addition, the outer housing which surrounds the spindle bearing housing at a distance acts as a shield against noise. In this manner, effective reduction of noise can be achieved without the requirement of providing rubber-elastic elements as holding devices between the spindle bearing housing and the spindle rail.
In certain preferred embodiments rubber elastic damping devices may be provided in addition between the bearing housing and outer housing, which bearing devices may therefore be designed exclusively for vibration damping without concern for holding the spindle in its position since that holding function is carried out by the vibration isolation connection of the bearing housing bottom part with the outer housing.
In certain preferred embodiments of the invention, it is provided that the connecting element has a material cross-section which differs from the material cross-section of the spindle bearing housing. This difference in the cross-section of the material inhibits the flow of the structure-borne sound. In this case, the inhibiting effect is the more pronounced, the larger the difference.
In certain preferred embodiments of the invention, it is provided that the vibration isolation connection includes a material, the modulus of elasticity of which differs from the modulus of elasticity of the material of the spindle bearing housing and/or the surrounding outer housing. This difference with respect to the modulus of elasticity of the two materials also results in a hindering of the flow of the structure-borne sound, the hindering also in this case being the higher, the larger the difference.
In certain preferred embodiments of the invention, it is provided that the vibration isolation connection includes a connecting element which is a spring element which is arranged as an axial extension of the spindle bearing housing and is essentially radially flexible with respect to the spindle axis. This spring element may act as a point of discontinuity in which case, on the one hand, in relationship to the spindle bearing housing, it may have a small material cross-section and, on the other hand, a clearly increased modulus of elasticity so that a particularly effective point of discontinuity is created.
In certain preferred embodiments of the invention, it is provided that the vibration isolation connection includes a connecting element in the form of a pin arranged as an axial extension of the spindle bearing housing which is connected with the spindle bearing housing and the surrounding housing and has a free length situated between the connecting points. A pin of this type, in a relatively simple manner, may be dimensioned such that it can reliably absorb the occurring forces while, on the other hand, it forms a very effective point of discontinuity.
In certain preferred embodiments of the invention, it is provided that the surrounding outer housing has a sleeve-type shape and is equipped with devices for the fastening to a spindle rail. In this embodiment, each spindle bearing housing is surrounded by its own housing.
In certain preferred embodiments of the invention, it is provided that several spindle bearing housings arranged in a row are housed inside a common housing. In an advantageous design of this further development, it is provided that the common housing is a spindle rail. As a result, the expenditures can be slightly reduced because a component which, as a rule, is present anyhow can also be used as the surrounding housing.
In certain preferred embodiments of the invention, the outer housing has a substantially greater axial moment of inertia than does the bearing housing. In especially preferred embodiments the axial moment of inertia of the outer housing is at least 10 times the axial moment of inertial of the spindle bearing housing.
Because of the ratio of the axial moments of inertia, vibrations of the spindle bearing housing are transmitted to the sleeve-type outer housing and by it to the spindle rail only to a significantly reduced extent. The ratio of the axial moments of inertia provides that the spindle bearing housing can virtually not excite the much stiffer sleeve-type outer housing to perform vibrations. The running noises are therefore essentially reduced to the running noises generated by the spindle bearing housing. In addition, because of its preferably relatively thick wall thickness, the sleeve-type outer housing acts as a shielding device. This results in a reduction of noise as well as in an insulating of noise.
In certain preferred embodiments of the invention, it is provided that the wall thickness of the sleeve-type outer housing amounts to at least four times the wall thickness of the spindle bearing housing. This results in a particularly good shielding. For the same purpose, it is advantageous if, according to another development of the invention, the sleeve-type outer housing extends at least along two thirds of the height of the spindle bearing housing.
In certain preferred embodiments of the invention, it is provided that the spindle bearing housing is equipped with a covering which reaches over the upper edge of the sleeve-type outer housing, preferably with play. As a result, a noise shielding is also obtained in the area of the upper edge of the ring gap between the spindle bearing housing and the sleeve-type housing.
In certain preferred embodiments of the invention, it is provided that the spindle bearing housing, beyond the step bearing, is lengthened in a tube shape and is held in this area by the sleeve-type outer housing. As a result, the possibilities of a vibration transmission between the spindle bearing housing and the sleeve-type outer housing can be further reduced. In addition, there is a simple shaping of the spindle bearing housing which, as a whole, consists of a tube-shaped body.
In certain preferred embodiments of the invention, it is provided that the area of the spindle bearing housing which receives the neck bearing outer race is constructed to be flexible in the radial direction. As a result, the area of the spindle shaft is reduced which may affect the spindle bearing housing in the area of the neck bearing. This also has an advantageous effect on the noise level.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.